Plant control composition and methods of use

ABSTRACT

Compositions and methods for vegetation control comprise synergistic combinations of a thiazol-urea abscission agent and an adduct formed by the reaction of sulfuric acid with an amide. The synergistic combinations are particularly useful for the defoliation of cotton.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to agents for controlling plant growth andmethods for their use and preparation. The invention particularlyrelates to a combination of an abscission agent and an amide-sulfuricacid adduct, which combination is characterized by synergisticdefoliation activity.

2. Description of the Art

Special tissue regions at the base of a leaf, flower or fruit stalk, areresponsible for the separation of plant organs such as leaves, flowersand fruit from the plant body. When the separation process begins, thecell walls in the separation zone become soft so that the separation ofthe organ (abscission) becomes possible through mechanical forces, forexample, by wind, or by weight of the organ itself. This, however, oftendoes not take place at the desired time or to a desired extent.Frequently, it is advantageous to achieve this process in a controlledmanner at a certain time or stage in the development of a plant.

Controlled defoliation is of special economic importance because of theeasier harvesting and accelerated ripening obtainable thereby inagricultural and horticultural crops. Abscission agents for inducingsuch defoliation, via hormonal regulation, are known. For example,thidiazuron, the common name for n-phenyl-n'-1,2,3-thiadiazol-5-yl urea,is a known cotton defoliant and has been registered for such purposewith the Environmental Protection Agency.

Defoliation also may be accomplished by leaf injury with certainherbicides. The herbicide may be of either the contact or systemicvariety. A contact herbicide requires that a substantial portion of theplant be contacted with the active ingredient of the herbicide beingapplied. A systemic herbicide translocates through the plant andsubstantial surface contact is not required.

Many chemical agents have been found which are useful for thedefoliation of plants, either through hormonal regulation or herbicidalinjury, and have been registered with the Environmental ProtectionAgency for certain selected uses. Their effectiveness frequently variesgreatly depending upon the climatic conditions, application rates, andthe plant to which they are being applied. Thus, there still is need foran improved agent for effectively defoliating plants to facilitateharvest, for the destruction of plants for weed control, and the like.

SUMMARY OF THE INVENTION

The present invention resides in the discovery that a combination of anabscission agent and an amide-sulfuric acid adduct exhibit substantiallyenhanced plant control activity. The combination has been found to bemore effective than when they are applied individually. This resultoften is termed potentiation or synergism since the combinationdemonstrates a potentency or activity level exceeding that which wouldbe expected based on knowledge of the individual potencies of thecomponents.

The abscission agent, as defined herein, is a plant tolerable agentwhich affects the cells at the base of the leaf stalk contacted. Theadduct component of the present invention is generally used as a contactherbicide to destroy plants. A particularly surprising aspect of thepresent invention is that the claimed combination of agents appears toact in a synergistic manner to effect plant control, for example, bydefoliation. In one very important discovery, it was found that theabscission agent and adduct could be used in combination in individuallow concentrations (or in individual low application rates) that wouldrender each essentially ineffective for its intended purpose--yetproduce, through the combination, a highly efficacious abscission agentfor defoliation. More specifically, when the abscission agent is appliedat a rate ineffective by itself for significant defoliation incombination with the adduct applied at a rate ineffective by itself forsignificant herbicidal activity, the result is an abscission agent ofhigh potency for defoliation. Accordingly, although the invention is notto be held to any theory of operation, it seems clear that in thecombination of the invention the adduct, for unknown reasons,substantially increases the potency of the abscission agent, allowingfor less of it to be used while still attaining the desired defoliationresult.

A particularly preferred composition of the present invention is acombination of thidiazuron and monocarbamide dihydrogen sulfate. Thepreferred combination has been found to be particularly effective forthe defoliation of cotton. In addition, post treatment regrowth ofleaves on a treated plant is substantially inhibited by the combinationof the present invention.

DETAILED DESCRIPTION OF THE INVENTION

It now has been found that synergism in the defoliation of plants isexhibited by a combination of a thiozol-urea abscission agent and anadduct produced by reaction of sulfuric acid and an amide. Thethiozol-urea abscission agents of the present invention arecharacterized by the general formula ##STR1## in which

R₁ and R₂ are independently selected from the group consisting of H₂ andC₁ to C₅ organic radicals, R₃ is a C₁ to C₅₀ organic radical, preferablyC₁ to C₂₀, more preferably C₁ to C₁₀, and X is an oxygen or sulfur atom.

Preferred compounds of the above general formula are those compounds inwhich the radical R₁ is hydrogen or alkyl with 1 to 3 carbon atoms, suchas methyl or ethyl, the radical R₂ is hydrogen or alkyl with 1 to 4carbon atoms, such as methyl or ethyl, the radical R₃ is alkyl with 1 to4 carbon atoms, such as methyl or ethyl, cycyoalkyl with 5 to 8 carbonatoms, such as cyclopentyl, cyclohexyl or methylcyclohexyl, or a phenyl,halphenyl, methylphenyl or methoxyphenyl radical, and X is oxygen orsulfur. Particularly preferred compounds are those in which the radicalsR₂ and R₃ jointly form with the N atom an morpholino, piperidino orpyrrolidino group.

Examples of methods for formulating such compounds are found in U.S.Pat. Nos. 4,294,605, issued Oct. 13, 1981, and 3,883,547, issued May 13,1975, which are incorporated herein in their entirety by reference.Exemplary compounds are set forth in Table A below in which the (D)following temperature refers to a decomposition temperature.

                  TABLE A                                                         ______________________________________                                        Active Substance       Physical Constant                                      ______________________________________                                        1.    N-phenyl-N'-(1,2,3-thiadiazole-                                                                    M.P. 217° C. (D)                                  5-yl) urea                                                              2.    N-ethyl-N-phenyl-N'-(1,2,3-                                                                        M.P. 200° C. (D)                                  thiadialol-5-yl) urea                                                   3.    N-(4-chlorophenyl)-N'-(1,2,3-                                                                      M.P. 256° C. (D)                                  thiadiazole-5-yl) urea                                                  4.    N-cyclohexyl-N-'-(1,2,3-                                                                           M.P. 215° C. (D)                                  thiadiazole-5-yl) urea                                                  5.    N-(chlorophenyl)-N'-(1,2,3-                                                                        M.P. 244° C. (D)                                  thiadiazole-5-yl) urea                                                  6.    N-(4-methylphenyl)-N'-(1,2,3-                                                                      M.P. 228° C. (D)                                  thiadiazole-5-yl) urea                                                  7.    N-(3-methylphenyl)-N'-(1,2,3-                                                                      M.P. 208° C. (D)                                  thiadiazole-5-yl) urea                                                  8.    N-(3,4-dichlorophenyl)-N'-(1,2,3-                                                                  M.P. 236° C. (D)                                  thiadiazole-5-yl) urea                                                  9.    N-methyl-N'-(1,2,3-  M.P. 174° C.                                      thiadiazole-5-yl) urea                                                  10.   N,N-dimethyl-N'-(1,2,3-                                                                            M.P. 222° C. (D)                                  thiadiazole-5yl) urea                                                   11.   N,N-dimethyl-N'-methyl-N'-                                                                         M.P. 129° C.                                      (1,2,3-thiadiazole-5-yl) urea                                           12.   N-methyl-N'-methyl-N'-(1,2,3-                                                                      M.P. 221° C.                                      thiadiazole-5-yl) urea                                                  813.  N-methyl-N-phenyl-N'-(1,2,3-                                                                       M.P. 184° C. (D)                                  thiadiazole-5-yl) urea                                                  14.   N-ethyl-N-phenyl-N'-(1,2,3-                                                                        M.P. 200° C. (D)                                  thiadiazole-5-yl) urea                                                  15.   N-propyl-N-phenyl-N'-(1,2,3-                                                                       M.P. 190° C. (D)                                  thiadiazole-5-yl) urea                                                  16.   N-butyl-N-phenyl-N'-(1,2,3-                                                                        M.P. 198° C. (D)                                  thiadiazole-5-yl) urea                                                  17.   N-(2-chlorophenyl)-N'-(1,2,3-                                                                      M.P. 237° C. (D)                                  thiadiazole-5-yl) urea                                                  18.   N-(2-methylphenyl)-N'-(1,2,3-                                                                      M.P. 197° C. (D)                                  thiadiazole-5-yl) urea                                                  19.   N-(2-nitrophenyl)-N'-(1,2,3-                                                                       M.P. 229° C. (D)                                  thiadiazole-5-yl) urea                                                  20.   N-(3-nitrophenyl)-N'-(1,2,3-                                                                       M.P. 252° C. (D)                                  thiadiazolyl-5-yl) urea                                                 21.   N-methyl-N-(2-methylphenyl)-N'-                                                                    M.P. 215° C. (D)                                  (1,2,3-thiadiazole-5-yl) urea                                           ______________________________________                                    

The adducts for use in accordance with the present invention areproduced by reacting sulfuric acid with an amide having the formula:##STR2## wherein X is a chalcogen, each of R₁, R₂ and R₃ isindependently selected from hydrogen and monovalent organic radicals,and R₁ and R₂, together, can form a divalent organic radical. The molarratio of amide to sulfuric acid is within the range of about 1/4 to lessthan 2 so that at least some of the sulfuric acid is present as themonoamide-sulfuric acid adduct. As used herein, "amide" includes allcomponents of formula (2) regardless of the chalcogen employed.

When R₁, R₂ and R₃ are organic radicals, they may be cyclic or acyclic,straight or branched chained and can contain one or more hetero atomssuch as sulfur, nitrogen, oxygen, phosphorus and the like. Further, theycan contain one or more substituents such as thiol, hydroxy, nitro,amino, nitrile, amide, ester and halogen groups and others. Such organicradicals may contain aryl groups, such as aralkyl and alkaryl groups.The preferred organic radicals are free of olefinic or alkynylunsaturation and generally have up to about 20, preferably up to about10 carbon atoms, particularly preferred amides are urea, thiourea,formamide, biuret, triuret, thioformamide, ethyl formamide, methylformamide, and combinations of these.

The chalcogens are elements of Periodic Group VI-B and include oxygen,sulfur, selenium, tellurium, and polonium. Oxygen and sulfur arepresently preferred due to low cost, availability, low toxicity andchemical activity, with oxygen the most preferred.

The combination of agents can be used for immediate and long-term, pre-and postemergent control of essentially any form of vegetation. Thecombination of agents of the present invention is particularly useful asa defoliating agent. It may be used, for example, in tree nurseries,fruit and vegetable cultivations, legumes, grapevines, roses, and inparticular, cotton. The plants or plant parts to be harvested arethereby made both more accessible in an advantageous manner and also areaccelerated considerably in their ripening. In certain cases and underproper environmental conditions, plants thus treated in time will reformsound, normal foliage.

The combination of agents of the present invention is particularlysuited for defoliating cotton plants, making it possible to an extentnot previously obtained to use picking machines for the harvest. It is aparticular advantage of the present invention that other defoliatingagents are not required. The claimed combination both defoliates thecotton plant and substantially inhibits regrowth of new leaves for asubstantial period of time. This latter aspect is particularly importantwhere the cotton cannot be harvested within a short time of treatment.

The combination of the present invention also may be used advantageouslyfor the control of vegetation. The efficacy for growth control depends,among other things, on the amount of the combination applied per acre,the treatment time, and the type of plant to which it is applied. Theinhibiting effects may occur in a manner which produces, for example,total inhibition of development (destruction) of a waste blend floralincluding shrubbery. The combination of agents of the invention also canbe used wherever it is desired not to fully destroy a floral at once,but to maintain it in a vegetative low growth stage.

Illustrative of vegetation that can be controlled by these methods, withor without the use of surfactants are: black mustard (brassica nigra),curly dock (rumex crispus), common groundsel (senecio vulgaris),pineapple weed (matricaria matricarioides), swamp smartweed (kelp)(polygonum coccineum), prickly lettus (lactuca scariola), lance-leavedgroundcherry (physalis lanceifolia), annual sowthistle (sonchusoleraceus), london rocket (sisybrium irio), common fiddleneck(aamsinckia intermedia), hairy nightshade (solanum sarrachoides),shepherd's purse (capsella bursa-pastoris), sunflower (helianthusannus), common knotweed (polygonum aviculare), green amaranth(amaranthus hybridus), mare's tail (conyza canadensis), henbit (lamiumamplexicaule), cocklebur (xanthium strumarium), cheeseweed (malvaparviflora), lambsquarters (chenopodium album), puncture vine (tribulusterrestris), common purslane (portulaca oleracea), prostrate spurge(euphorbia supina), telegraph plant (heterotheca grandiflora),carpetweed (mollugo verticillata), yellow starthistle (centaureasolstitialis), milk thistle (silybum marianum), mayweed (anthemiscotula), burning nettle (urtica urens), fathen (atriplex patula),chickweed (stellaria media), scarlet pimpernel (ana--gallis arvensis)redroot pigweed (amaranthus retroflexus), minnerslettuce (montiaperfoliata), turkey mullein (eremocarpus setigerus), nettleleafgoosefoot (chenopodium murale), prostrate pigweed (amaranthusblitoides), silverleaf nightshade (solanum elaeagnifoli-um), hoary cress(cardaria draba), largeseed dodder (cuscuta indecora), Californiaburclover (medicago polymorpha), horse purslane (trianthemaportula-castrum), field bindweed (Iconvolvulus arvensis), Russianknapweed (centaurea repens), flax-leaved fleabane (conyza bonariensis),wild radish (raphanus sativus), tumble pigweed (amaranthus albus),stephanomeria (stephanomeria exiqua), wild turnip (brassica campestris),buffalo goard (cucurbita foetidissima), common mullein (verbascumthapsus), dandelion (taraxacum officinale), Spanish thistle (xanthiumspinosum), chicory (cichorium intybus), sweet anise (foeniculumvulgare), annual yellow sweetclover (melilotus indica), poison hemlock(conium maculatum), broadleaf filaree (erodium botrys), whitestemfilaree (erodium moschatum), redstem filaree (erodium cicutarium),ivyleaf morning-glory (ipomea hederacea), shortpod mustard (brassicageniculata), buckhorn plantain (plantago lacenolata), sticky chickweed(cerastium viscosum), himalaya blackberry (rubus- procerus), purslanespeedwell (veronica peregrina), Mexican tea (chenopodium ambrosioides),Spanish clover (lotus purshianus), Australian brassbuttons (cotulaaustralis), goldenrod (solidago californica), citron (citrulluslanatus), hedge mustard (sisymbrium orientale), black nightshade(solanum nodiflorum), Chinese thornapple (datura ferox), bristly oxtongue (picris echioi-des), bull thistle (cirsium vulgare), spinysowthistle (sonchus asper), Tasmanian goosefoot (chenopodium pumilio),goosefoot (chenopodium botrys), wright groundcherry (physalisacutifolia), tomatillo groundcherry (physalis philadelphica), prettyspurge (euphorbia peplus), bitter apple (cucumis myriocarpus), indiantobacco (nicotiana bigelovii), common morning-glory (ipomoea purpurea),waterplantain (alisma triviale), smartweed (polygonum lapathifolium),mature sowthistle (sonchus asper), yellow nutsedge (cyperus esculentus),purple nutsedge (cyperus rotundus), lupine (lupinus formosus), andgrasses of the family Gramineae such as annual rye grass, blue grass,water grass, barnyard grass, bermuda grass, fescue, mat grass, Johnsongrass, and the like.

The amide-sulfuric acid adduct can be produced by the reaction of theamide with sulfuric acid by the methods described in U.S. Pat. No.4,445,925, the disclosure of which is incorporated in its entirety byreference.

While the combination of the present invention can be used alone, itgenerally is applied to plants in conjunction with other substances,such as a carrier vehicle, wetting agents, emulsifiers, solvents and thelike. Suitable carrier vehicles include water, aliphatic or aromatichydrocarbons, such as benzene, toluene, xylene, cyclohexonone,isophorone, and mineral oil fractions. The particularly preferredcarrier vehicle is water, based on its availability and cost.Alternatively, of course, a solid carrier vehicle could be utilized.Examples of solid carrier vehicles are minerals, such as siliceous clay,silica gel, talc, kaolin, limestone, and plant products, such as flours.

Typical surface active substances, which may be utilized includedcalcium-lignin sulfonate, polyoxyethyleneoctlphenol ether andnaphthalene-solfonic acids and their salts, phenosulfonic acids andtheir salts, formaldehyde condensates, fatty alcohol sulfates, andsubstituted benenesulfonic acids and their salts.

The proportions of the active agents in the composition of the presentinvention may vary within wide limits. For example, the composition maycontain from about 10 to 80 weight percent of the active agents, andabout 20 to 90 weight percent of a solid or liquid carrier vehicle, andoptionally up to 20 weight percent of a surface-active substance.

The ratio of adduct to abscission agent also may vary widely. Theabscission agents, for use in the present invention, are typically inthe form of powder, whereas the adduct is generally in the form of aliquid. Accordingly, the ratios are expressed in terms of a volume ofadduct to a given weight of abscission agent. Broadly, the ratio ofadduct to abscission agent is in the range of from about one quart ofadduct per pound of abscission agent to as high as about 40 quarts ofadduct per pound of abscission agent. More typically, the ratio will bewithin the range of from about 2.5:1 to 20:1, with a preferred rangebeing from about 8:1 to 13:1 (quarts per pound) based on the activeingredient.

The combination of the present invention has been found to be highlyeffective for defoliation of plants, such as cotton, when the ratio ofthe adduct to abscission agent is selected such that, when applied, theamount of adduct applied per acre is within the range of from about 0.25to 10 quarts, preferably from .5 to 4 quarts, and more preferably withinthe range of from about 0.1 to 2 quarts per acre. In a similar manner,the combination is most effective when the abscission agent is appliedin an amount to provide from about 0.01 to 0.3 pounds per acre,preferably from 0.05 to 0.2 pounds per acre, and more preferably about0.075 to 0.15 pounds per acre.

To facilitate a uniform distribution of the composition of the inventionon plants to be treated, it generally is applied in a carrier vehicle.As hereinbefore mentioned, water is the preferred carrier vehicle. Whenthe composition is sprayed from the ground, typically, it is dilutedwith water to provide a spray volume of from 10 to 50, and moretypically 15 to 30 gallons per acre. In the case of aerial spraying, amore concentrated solution is used and is applied at the rate of fromabout 2 to 8, and more generally 3 to 5 gallons per acre.

The following example and test data therein are for illustrativepurposes only and should not be construed as limiting the scope of theinvention.

EXAMPLE

To demonstrate the efficacy of the present invention, a series of fieldtests was performed. The abscission agent utilized was thidiazuron, soldcommercially in the form of a wettable powder and containingapproximately 50 weight percent of the active ingredient. It is sold foruse as a cotton defoliant and registered for such purpose with theEnvironmental Protection Agency. The adduct used is a commerciallyavailable monocarbamide dihydrogen sulfate (MCDS) herbicide registeredwith the Environmental Protection Agency for use on a variety of plants.It is sold in a liquid form and generally comprises about 82 weightpercent of the active ingredient. Each was applied alone and in variouscombinations to cotton plants. The plants were approximately 30 inchestall having approximately 60 percent open boll. In each instance, theagents were diluted with water to provide a spray volume ofapproximately 25 gallons per acre.

Visual ratings of the percent defoliation obtained were made seven daysafter treatment (DAT). The results are set forth in Table 1.

                  TABLE 1                                                         ______________________________________                                                                        7 DAT                                         No.     Treatment        Rep    % Defol.                                      ______________________________________                                        1       MCDS (2 gal.)    1      25                                                                     2      20                                                                     3      20                                                                     Avg.   22                                            2       MCDS (3 gal.)    1      35                                                                     2      30                                                                     3      25                                                                     Avg.   30                                            3       MCDS (5 gal.)    1      35                                                                     2      25                                                                     3      30                                                                     Avg.   30                                            4       MCDS (10 gal.)   1      65                                                                     2      50                                                                     3      40                                                                     Avg.   52                                            5       Thidiazuron (0.1 lb.)                                                                          1      40                                                                     2      35                                                                     3      35                                                                     Avg.   37                                            6       Thidiazuron (0.2 lb.)                                                                          1      50                                                                     2      40                                                                     3      50                                                                     Avg.   47                                            7       MCDS & Thidiazuron                                                                             1      90                                                    (1 gal. + 0.1 lb.)                                                                             2      98                                                                     3      95                                                                     Avg.   94                                            8       MCDS & Thidiazuron                                                                             1      95                                                    (1 gal. + 0.2 lb.)                                                                             2      90                                                                     3      98                                                                     Avg.   94                                            9       MCDS & Thidiazuron                                                                             1      95                                                    (2 gal. + 0.1 lb.)                                                                             2      95                                                                     3      98                                                                     Avg.   96                                            10      MCDS & Thidiazuron                                                                             1      98                                                    (2 gal. + 0.2 lb.)                                                                             2      95                                                                     3      95                                                                     Avg.   96                                            11      MCDS & Thidiazuron                                                                             1      98                                                    (3 gal. + 0.1 lb.)                                                                             2      95                                                                     3      95                                                                     Avg.   96                                            12      MCDS & Thidiazuron                                                                             1      95                                                    (3 gal. + 0.2 lb.)                                                                             2      98                                                                     3      90                                                                     Avg.   94                                            ______________________________________                                    

For purposes of cotton defoliation, any percent defoliation of less than90 percent generally is deemed unacceptable by the growers. From Table1, it is seen that monocarbamide dihydrogen sulfate (MCDS), even whenapplied in amounts as high as 10 gallons per acre, does not producesatisfactory defoliation. In a similar manner, thidiazuron when appliedin amounts of from 0.1 to 0.2 pounds per acre provide inadequatedefoliation. However, in all instances, the combination of monocarbamidedihydrogen sulfate (MCDS) and thidiazuron resulted in excess of 90percent defoliation. It is believed the foregoing table clearlydemonstrates the synergistic effect of the claimed combination.

In addition, it should be noted that the rate at which the commercialformulations of monocarbamide dihydrogen sulfate normally is applied isfrom a minimum of 5 up to as high as 20 gallons per acre. In a similarmanner, the normal or recommended application rate for commercialformulations of thidiazuron is from about 0.2 of a pound up to about 0.4pound per acre for defoliation. As shown in Table I, the application of0.10 pound of thidiazuron produced only 37 percent defoliation(treatment No. 5). One gallon of monocarbamide dihydrogen sulfate wouldhardly produce any visible results on cotton. Indeed, as shown bytreatment No. 1, 2 gallons per acre results in only 22 percentdefoliation. Nonetheless, as shown by treatment No. 7, 1 gallon ofmonocarbamide dihydrogen sulfate and 0.10 pound of thidiazuron producedsubstantially in excess of 90 percent defoliation.

A second field test was conducted to verify the results obtained above.The same agents were utilized and diluted to provide the same 25 gallonper acre application rate. The results of this second field test are setforth in Table II. From that Table it is seen, again, that the claimedcombination exhibits a synergistic effect and provides in excess ofabout 90 percent defoliation.

                  TABLE II                                                        ______________________________________                                                           % Defoliation                                                                           6     10    14                                   No.  Treatment       Rep     DAT   DAT   DAT                                  ______________________________________                                        1    Thidiazuron     1       20    50    60                                        (0.10 lb.)      2       25    40    60                                                        3       20    40    60                                                        Avg.    22    43    60                                   2    Thidiazuron     1       35    70    85                                        (0.20 lb.)      2       30    75    90                                                        3       35    70    85                                                        Avg.    33    72    87                                   3    MCDS + Thidiazuron                                                                            1       90    95    98                                        (2 qt. + 0.1 lb.)                                                                             2       80    80    95                                                        3       95    95    90                                                        Avg.    88    90    94                                   4    MCDS + Thidiazuron                                                                            1       90    98    98                                        (4 qt + 0.1 lb.)                                                                              2       98    98    98                                                        3       95    98    98                                                        Avg.    94    98    98                                   5    MCDS + Thidiazuron                                                                            1       90    95    98                                        (8 qt. + 0.1 lb.)                                                                             2       90    90    95                                                        3       95    95    98                                                        Avg.    92    93    97                                   ______________________________________                                    

A third field test was conducted to determine the effect of varying theratio of adduct to abscission agent. The adduct and abscission agentutilized were the same as in the previous test. In each instance, theywere further diluted with water to provide an application rate of 25gallons per acre. The cotton treated was immature and actively growingwhich is more difficult to defoliate and inhibit regrowth. Leaf countswere taken three and seven days after treatment (DAT). Application No.16 was a material currently considered by the growers as a standardagainst which other formulations are judged. It comprised a mixture of20 oz. tribufos (an organo phosphate defoliant) and a small amount ofthidiazuron (.063 pounds active ingredient) per acre. The organophosphate is the principal defoliant, and the thidiazuron is used toinhibit regrowth of leaves. While the organo phosphates are effectivedefoliants, they have an unpleasant odor and have been subject to someenvironmental concern. Thus, a replacement for the organo phosphates isdesirable.

The results of the test set forth in Tables III and IV clearlydemonstrate the efficacy of the present invention over a wide range ofratios. More particularly, from those tables, it is seen that theclaimed combination is as effective or more effective in defoliatingcotton plants than the standard. Specifically, the average number ofleaves remaining on the plants is approximately equal to or less thanthe average number of leaves on plants treated with the "standard"defoliant.

                  TABLE III                                                       ______________________________________                                        Rate/Acre.sup.3   3 DAT                                                       Commercial Formulation                                                                          # Leaves/Plant.sup.2                                        No.  MCDS    Thidiazu Ratio.sup.1                                                                         I    II   III  IV   Avg                           ______________________________________                                         1    8 oz   0.050 lb.                                                                              5:1   4.6  4.4  4.8  5.2  4.75                           2    16     0.10           4.0  3.0  4.4  3.6  3.75                           3    32     0.20           2.6  4.0  4.2  4.4  3.80                           4    16     0.05     10:1  3.8  4.8  3.4  3.0  3.75                           5    32     0.10           2.6  2.2  2.8  3.2  2.70                           6    64     0.20           3.6  3.0  2.0  2.0  2.65                           7    24     0.05     15:1  3.0  3.0  3.6  2.8  3.10                           8    48     0.10           2.4  2.8  2.2  3.2  2.65                           9    96     0.20           3.0  3.0  3.0  1.8  2.70                          10    32     0.050    20:1  4.2  3.0  3.6  2.4  3.30                          11    64     0.10           2.4  2.4  2.6  2.4  2.45                          12   128     0.20           3.2  2.2  3.0  2.4  2.70                          13    0      0.050    0:1   7.2  8.2  6.4  6.8  7.15                          14    0      0.10           5.8  3.4  4.4  3.8  4.35                          15    0      0.20           3.4  4.0  4.4  4.6  4.10                          16    STD    0.063    n/a   4.4  4.4  4.6  5.2  4.65                                20 oz.                                                                  ______________________________________                                         .sup.1 Ratio of qts MCDS:lb of commercial 50 weight percent thidiazuron       (formulation:formulation).                                                    .sup.2 The average was computed from a total of 20 observations (4            replicates × 5 observations each). Observations consisted of            randomly selecting five plants from the middle two rows of each plot and      counting the remaining primary leaves (axillary branches and leaves were      NOT counted).                                                                 .sup.3 Commercial formulation = 81.6 wt. percent active ingredient MCDS       and 50 wt. percent active ingredient thidiazuron.                        

                  TABLE IV                                                        ______________________________________                                        Rate/Acre.sup.3   7 DAT                                                       Commercial Formulation                                                                          # Leaves/Plant.sup.2                                        No.  MCDS    Thidiazu Ratio.sup.1                                                                         I    II   III  IV   Avg                           ______________________________________                                         1    8 oz   0.050 lb.                                                                              5:1   4.5  3.3  3.7  3.5  3.75                           2   16      0.10           2.3  2.7  2.7  1.7  2.35                           3   32      0.20           1.8  1.7  1.0  2.7  1.80                           4   16      0.05     10:1  2.5  3.2  2.0  2.5  2.55                           5   32      0.10           0.3  1.3  0.7  0.7  0.75                           6   64      0.20           2.0  2.0  0.5  0.8  1.33                           7   24      0.050    15:1  2.2  2.7  2.0  1.2  2.03                           8   48      0.10           0.7  0.5  0.2  0.5  0.48                           9   96      0.20           1.5  1.3  1.7  1.7  1.55                          10   32      0.050    20:1  2.7  3.0  1.0  3.0  2.43                          11   64      0.10           0.5  1.2  0.3  0.3  0.58                          12    8      0.20           1.8  1.7  1.8  2.3  1.90                          13    0      0.050    0:1   5.0  6.5  5.0  4.5  5.25                          14    0      0.10           3.7  2.7  3.7  3.0  3.28                          15    0      0.20           2.5  3.0  3.0  2.5  2.75                          16   STD     0.063    n/a   3.5  3.0  3.5  4.0  3.50                          ______________________________________                                         .sup.1 Ratio of qts MCDS:lb of commercial 50 weight percent thidiazuron       (formulation:formulation).                                                    .sup.2 The average was computed from a total of 24 observations (4            replicates × 6 observations each). Observations consisted of            randomly selecting six plants from the middle two rows of each plot and       counting the remaining primary leaves (axillary branches and leaves were      NOT counted).                                                                 .sup.3 Commercial formulation = 81.6 wt. percent active ingredient MCDS       and 50 wt. percent active ingredient thidiazuron.                        

While particular embodiments of this invention have been described, itwill be understood that the invention is not limited thereto. Manymodifications can be made. For example, while the invention has beendescribed with respect to the two particularly preferred compounds, andtheir use on cotton, it will be readily apparent to those skilled in theart that other combinations within the scope of the invention can beutilized on cotton and on other plants as well. It is intended that suchmodifications as will fall within the spirit and scope of the appendedclaims are included.

What is claimed is:
 1. A composition for controlling vegetationcomprising thidiazuron and monocarbamide dihydrogen sulfate.
 2. Thecomposition of claim 1 wherein the abscission agent and adduct arepresent in an amount to provide a ratio of adduct to abscission agentwithin the range of from about 1 quart of adduct per pound of abscissionagent to 40 quarts of adduct per pound of abscission agent.
 3. Thecomposition of claim 2 further including from about 20 to 90 wt. percentof a carrier vehicle.
 4. The composition of claim 3 wherein the carriervehicle is water.
 5. A mixture of thidazuron, monocarbamide dihydrogensulfate and water.
 6. A method for controlling vegetation comprising thestep of applying to the vegetation an effective amount of a compositionformed by mixing thidiazuron and monocarbamide dihydrogen sulfate. 7.The method of claim 6 wherein the vegetation is a cotton plant and thecomposition is applied in an effective amount to defoliate the plant.